U.S. patent application number 11/403173 was filed with the patent office on 2006-08-24 for apparatus for disinfecting fluid using ultraviolet radiation.
This patent application is currently assigned to Honeywell International Inc.. Invention is credited to Robert J. Saccomanno.
Application Number | 20060186059 11/403173 |
Document ID | / |
Family ID | 34972847 |
Filed Date | 2006-08-24 |
United States Patent
Application |
20060186059 |
Kind Code |
A1 |
Saccomanno; Robert J. |
August 24, 2006 |
Apparatus for disinfecting fluid using ultraviolet radiation
Abstract
Ultraviolet radiation is used to disinfect water or a fluid in a
flow tube, where the flow tube acts as a fluid filled light guide
for the ultraviolet radiation and the ultraviolet radiation
propagates through the flow tube via total internal reflection.
Inventors: |
Saccomanno; Robert J.;
(Montville, NJ) |
Correspondence
Address: |
Honeywell International Inc.;Patent Services
Post Office Box 2245
Morristown
NJ
07962-2245
US
|
Assignee: |
Honeywell International
Inc.
Morristown
NJ
|
Family ID: |
34972847 |
Appl. No.: |
11/403173 |
Filed: |
April 12, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10874293 |
Jun 22, 2004 |
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11403173 |
Apr 12, 2006 |
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10268567 |
Oct 9, 2002 |
6773584 |
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10874293 |
Jun 22, 2004 |
|
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60330174 |
Oct 17, 2001 |
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Current U.S.
Class: |
210/748.11 ;
210/748.13 |
Current CPC
Class: |
B01D 53/8675 20130101;
A61L 9/20 20130101; C02F 2201/3221 20130101; F24F 8/22 20210101;
A61L 2/10 20130101; C02F 1/325 20130101; C02F 2201/3228 20130101;
C02F 2201/326 20130101 |
Class at
Publication: |
210/748 |
International
Class: |
C02F 1/32 20060101
C02F001/32 |
Claims
1. A liquid light pipe based fluid purification system comprising a
cladding mechanism defining the wall of a liquid light pipe within
which the fluid is to be purified, the fluid flowing within the
liquid light pipe wall having a refractive index greater than the
refractive index of said cladding mechanism defining the wall of
the liquid light pipe, and a source of ultraviolet energy directing
ultraviolet radiation into the fluid within the liquid light pipe,
the ultraviolet radiation being guided within the liquid light pipe
via total internal reflection due to the differences in the
refractive indices of said fluid and said cladding mechanism
defining the wall of the liquid light pipe.
2. The liquid light pipe based purification system in accordance
with claim 1 wherein the respective refractive indices define a
numerical aperture of the liquid light pipe within the range of
wavelengths of the ultraviolet radiation used for the
purification.
3. The liquid light pipe based purification system in accordance
with claim 1 wherein said cladding mechanism comprises a UV-grade
glass or polymer pipe and an air gap adjacent said pipe.
4. The liquid light pipe based purification system in accordance
with claim 3 further comprising a strengthening support element
within said air gap.
5. The liquid light pipe purification system in accordance with
claim 1 wherein said cladding mechanism comprises a stainless steel
support structure supporting UV sidewall glass plates located in
grooves within the sidewalls of said support structure.
6. The liquid light pipe bases purification system in accordance
with claim 1 further comprising a strengthening support element in
contact with the exterior of said cladding mechanism.
7. An apparatus for purifying a fluid and comprising a cladding
tube through which the fluid to be purified is channeled, the fluid
having a refractive index greater than the refractive index of said
cladding tube, and a source of ultraviolet energy positioned to
couple ultraviolet radiation into the fluid within said cladding
tube, said ultraviolet radiation being guided through said cladding
tube via total internal reflection due the differences of
refractive indices.
8. A method for purifying a fluid by ultraviolet radiation, said
method comprising directing the fluid through a liquid light pipe
structure, the fluid having a greater refractive index than the
light pipe structure within a range of wave lengths of the
ultraviolet radiation, whereby the ultraviolet radiation travels
within the liquid light pipe structure by total internal
reflection.
9. The method in accordance with claim 7 wherein the liquid light
pipe structure comprises a glass or a non-absorbing polymer
material and an adjacent air gap.
10. The method in accordance with claim 8 wherein a strengthening
support element is inside said air gap.
11. The method in accordance with claim 7 wherein the liquid light
pipe structure comprises a support structure having UV glass plates
located within grooves in the sidewalls of the support structure.
Description
RELATED APPLICATIONS
[0001] This application a continuation of my application Ser. No.
10/874,293, filed Jun. 22, 2004, and which in turn is a
continuation-in-part of my application Ser. No. 10/268,567, filed
Oct. 9, 2002, now U.S. Pat. No. 6,773,584, Aug. 10, 2004, and which
is entitled to the benefit of Provisional Application Ser. No.
60/330,174, filed Oct. 17, 2001.
BACKGROUND OF THE INVENTION
[0002] 1. Technical Field
[0003] This invention relates to a water purification system using
intense ultraviolet irradiation to break down chemical bonds in
toxic compounds and to de-activate pathogens. The method can also
be applied to any mass transport, including the purification of
air. These systems can be applied to purify fluids containing
naturally occurring toxins or those resulting from biological and
chemical agents used in warfare.
[0004] 2. Background Art
[0005] The first application of an ultraviolet (UV) low-pressure
mercury vapor discharge lamp to disinfect water was in Marseilles,
France in 1901. However, it was not until 1955 that UV disinfection
became widely applied in Europe for potable water. In that year UV
disinfection equipment was installed in Switzerland, Austria and
Norway. Following the discovery of the formation of halogenated
hydrocarbons during chlorination, UV disinfection since became
popular in most European countries.
[0006] U.S. Pat. No. 1,196,481, issued Aug. 29,1916 described the
use of a mercury vapor lamp to generate sufficient ultraviolet
light (mostly 254-nm wavelength) to purify water. Further
refinements have been made over the years, such as in Ellner U.S.
Pat. No. 3,182,193 issued May 4, 1965, Maarschalkerweerd U.S. Pat.
No. 4,482,809 issued Nov. 13, 1984, Moyher U.S. Pat. No. 5,069,782
issued Dec. 3, 1991, Tiede U.S. Pat. No. 5,393,419 issued Feb.
28,1995, and Anderson U.S. Pat. No. 6,099,799 issued Aug. 8, 2000.
Much of the latter art referenced above improved upon aspects
related to commercial viability, such as improving UV dosage
uniformity through the use of baffles, UV-transparent coils, and
controlled turbulence; increasing UV intensity for higher flow
rates by increasing the number of lamps in a given volume; and
improving maintenance through the use of Teflon coatings, wiper
mechanisms, and adding turbulence.
[0007] Central to the present invention is the maximization of UV
contact-time with the water, as opposed to being absorbed by the
walls of the container.
[0008] It'swell known to those familiar with the art that many of
the UV water disinfecting systems utilize stainless steel water
jackets, owing at least in part to its history of use in fluid
applications requiring sanitary operation. It's viability as an
efficient UV reflector, however, is marginal, with data showing
less than 40% reflectance at normal for the germicidal wavelengths
around 250 nm (J. Zwinkels, et al, pgs 7933-7944, Applied Optics,
Vol. 33, No. 34, 1-Dec.-1994).
[0009] Prior art portable UV disinfection systems are described,
for example, in U.S. Pat. No. 5,900,212 as well as PCT publication
WO 01/28933. The '212 utilizes a portable UV source placed in a
container whose walls are of unknown reflectance. In the PCT
publication, a UV-transparent window allows sunlight through, only
to strike the container walls, again of unkown reflectance.
[0010] Improvements in reflectance is discussed in Stanley Jr, U.S.
Pat. No. 5,413,768, whereby water is guided through a high tensile
strength container having an interior surface that is highly
reflective to UV (such as aluminum). The container is further lined
with an FEP layer up to 10 mm thick and anchored to the container,
for example via ridges formed by routing the interior of the
container. While FEP is generally thought to be transmissive in the
UV, it will be shown that thick layers are in fact absorptive.
[0011] It will be shown that in applications where the water being
irradiated is "polished", the walls of prior art systems absorb a
high proportion of the incident UV.
[0012] It will also be shown that in the present invention, there
is substantial efficiency benefits in using total internal
reflection as the primary means of maximizing contact time between
UV and the fluid.
SUMMARY OF THE INVENTION
[0013] My invention is an apparatus and method for disinfecting
water, or other fluid, that channels water through a tube and
couples ultraviolet (UV) energy from a high intensity lamp into the
tube in a direction generally parallel to the flow of water. The
water, or other fluid, acts like the core of a liquid light
pipe/guide, with a low index cladding surrounding the water, either
via a low-index coating inside a tube, an air gap adjacent to a
UV-transparent tube, or some other cladding mechanism as is known
in the art of liquid light guides, such as that taught in U.S. Pat.
No. 4,009,382, U.S. Pat. No. 6,163,641, U.S. Pat. No. 6,418,257,
U.S. Pat. No. 6,507,688 and WO00/10044. In the case where the
cladding is not deposited on the inside of the tube, then the tube
itself is constructed of a non-UV-absorbing material, such as
UV-grade fused silica glass or a non-absorbing polymer tubing
(optionally reinforced to preclude bursting, for example as taught
in U.S. Pat. No. 5,371,934 and U.S. Pat. No. 6,620,190).
Advantageously, the use of light-pipe technology, which is based on
total internal reflection (TIR), ensures that all the input UV
radiation is dissipated in the water. Preferably, the tube is
polygonal in cross-section which is known, for example in the art
of projection display systems, to maximize light flux uniformity
within a light pipe over a shorter distance than one having a
circular cross section.
[0014] Embodiments of my invention with multiple zones efficiently
handle a wide range of water absorption coefficients, all at the
highest practical efficiency. In accordance with an aspect of one
embodiment of my invention, as disclosed in my patent application,
one of three zones is defined by a concentric UV-grade tubing
concentrically around only a portion of the tube through which the
water flows and others of these zones are defined between these
tubes and the enclosing outer tube.
[0015] In a second embodiment of my invention, in which fluid
enters at one end of my apparatus and exits at the other end, an
air gap surrounds the entire inner tube through which the water
flows. The total internal reflections in accordance with my
invention are assured by the relative refractive indices of the
fluid, the inner tube defining the fluid chamber through which the
fluid flows, and the gap between that inner tube and the inner
surface of the outer housing.
[0016] In a third embodiment of my invention the fluid chamber
through which the fluid to be disinfected flows comprises a hollow
helical coil, with the ultraviolet radiation being guided through
the hollow helical coil by total internal reflection. In this
embodiment the ultraviolet radiation can be introduced by a
side-coupled source of the ultraviolet radiation. To ensure maximum
efficiency, the bend radius of the hollow helical coil is
sufficiently greater than the coil diameter, a parameter known to
affect light leakage in the art of fiber optics.
[0017] In a further embodiment of my invention, a portable canteen
system comprises a container for an untreated fluid, such as water,
with the outlet from the container passing through a cap that
comprises a coiled tubing into which ultraviolet radiation is
launched, the radiation being guided through the coiled tubing by
total internal reflection, in accordance with my invention.
[0018] In accordance with an aspect of my invention, the relative
refractive indices are such that the ultraviolet radiation proceeds
within the fluid chamber of the various embodiments of my invention
substantially solely by total internal reflection. Specifically,
the water or other fluid to be treated has a refractive index of n1
and the wall or walls defining the fluid chamber have a refractive
index of n2, with n2 being less than n1. The refractive indices can
be considered to define a numerical aperture, where the term
`numerical aperture` describes the ability in an optical system to
accept rays. The ultraviolet radiation coupled into the apparatus
of my invention is substantially within the numerical aperture
defined by the relative refractive indices n1 and n2.
BRIEF DESCRIPTION OF DRAWINGS
Brief Description of the Several Views of the Drawing
[0019] FIG. 1 depicts an apparatus for disinfecting water using
ultraviolet radiation (UV) in accordance with one illustrative
embodiment of my invention.
[0020] FIG. 2 depicts a sectional view of the UV disinfecting
apparatus of FIG. 1.
[0021] FIG. 3 depicts a light pipe irradiation zone within the UV
disinfecting apparatus of FIG. 1, showing how the ultraviolet
radiation is contained using total internal reflection (TIR).
[0022] FIG. 4 depicts an apparatus for purifying or disinfecting a
fluid, such as water, using ultraviolet radiation in accordance
with a second illustrative embodiment of my invention.
[0023] FIG. 5 depicts a sectional view of FIG. 4.
[0024] FIG. 6 depicts an embodiment comprises plate-like elements
as opposed to the constructions shown in FIGS. 3 & 5.
[0025] FIG. 7 depicts a coiled-configuration showing UV entering
via a side-coupling optic
[0026] FIG. 8 depicts a canteen using a coiled-configuration
[0027] FIG. 9 depicts the characteristics of a xenon flash lamp,
water, and various materials (glass, fluoropolymer, and nucleic
acid) over UV wavelengths
[0028] FIG. 10 shows the attenuation of UV intensity over distance
as it travels through various types of reflective containers with
an average path length of 4.5 inches.
[0029] FIG. 11 shows the attenuation of UV intensity over distance
as it travels through various types of reflective containers with
an average path length of 2.25 inches.
LIST OF REFERENCE NUMBERS FOR THE MAJOR ELEMENTS IN THE
DRAWINGS
[0030] The following is a list of the major elements in the
drawings in numerical order. [0031] 1 incidence angle (refraction
at fluid inlet tube internal surface) [0032] 2 internal reflection
angle (reflection at fluid inlet tube external surface) [0033] 5
fluid (to be disinfected) [0034] 10 fluid inlet tube [0035] 11
entrance end (fluid inlet tube) [0036] 12 exit end (fluid inlet
tube) [0037] 13 internal surface (fluid inlet tube) [0038] 14
external surface (fluid inlet tube) [0039] 15 concentric gap
(between inlet tube and optical cladding tube) [0040] 20 optical
cladding tube [0041] 30 fluid containment vessel [0042] 31
ultraviolet mirror (fluid containment vessel internal surface)
[0043] 32 air gap (fluid containment vessel) [0044] 33 inner tube
(of fluid containment vessel) [0045] 35 ultraviolet inlet aperture
[0046] 36 lower ultraviolet window surface [0047] 37 upper
ultraviolet window surface [0048] 40 high intensity ultraviolet
lamp [0049] 50 fluid outlet tube [0050] 71 first UV light ray
(exiting lower ultraviolet window surface) [0051] 72 second UV
light ray (exiting fluid) [0052] 73 third UV light ray (entering
fluid inlet tube internal surface) [0053] 74 fourth UV light ray
(exiting fluid inlet tube internal surface) [0054] 75 fifth UV
light ray (entering fluid) [0055] 80 vessel [0056] 81 inlet nozzle
(of vessel) [0057] 83 exit port (of vessel) [0058] 85 surface
(inner wall) [0059] 86 inner UV transmissive tube [0060] 87 window
[0061] 88 lamp [0062] 75 fifth UV light ray (entering fluid) [0063]
100 light pipe (formed from fluid, fluid inlet tube, and concentric
gap) [0064] 101 stainless steel support structure [0065] 181
aperture shaped water inlet [0066] 182 aperture shaped water outlet
[0067] 185 UV sidewall glass mirror [0068] 186 mirror coated UV
window [0069] 187 apertured aluminum mirror coated UV window [0070]
188 ultraviolet radiation source [0071] 191 pressurized water
cavity [0072] 202 non-UV absorbing coupling prism [0073] 210 coiled
tubing (high refractive index) [0074] 220 surrounding medium (low
refractive index) [0075] 281 water inlet (to coiled tubing) [0076]
282 water outlet (from coiled tubing) [0077] 295 input UV radiation
[0078] 300 canteen [0079] 301 screw cap (for canteen) [0080] 302
fill tube (p/o canteen) [0081] 303 air vent tube (p/o canteen)
[0082] 304 water-blocking/air-passing membrane vents (cover air
vent tube) [0083] 310 coiled tubing (high refractive index) [0084]
381 water inlet (to coiled tubing) [0085] 391 water (contained
within canteen) [0086] 392 air (introduced into canteen) [0087] r
ratio of bend radius of the coil to radius of (coiled) tubing
[0088] R light pipe (formed from fluid, fluid inlet tube, and
concentric gap)
DESCRIPTION OF THE INVENTION
[0088] Mode(s) for Carrying Out the Invention
[0089] Referring first to FIG. 1, the basic construction of an
ultraviolet (UV) water disinfecting device in accordance with a
first embodiment of my invention is shown, including a fluid inlet
tube 10 that acts as a central light pipe, an optical cladding tube
20 around the lower portion of fluid inlet tube 10 and defining
therewith a concentric gap 15 (seen in FIG. 2), a fluid containment
vessel 30, a fluid outlet tube 50, and a high intensity UV lamp 40,
such as a flashlamp.
[0090] Referring next to FIG. 2, the fluid containment vessel 30
includes an internal surface configured as an ultraviolet mirror
31; for example, the fluid containment vessel may be constructed
from aluminum and the internal surface may be polished aluminum. A
fluid 5 to be disinfected, such as water, enters the fluid inlet
tube 10 through an entrance end 11. The fluid inlet tube 10 may be
manufactured, for example from UV-grade fused silica.
[0091] The fluid 5 travels through the fluid inlet tube 10 towards
the high intensity UV lamp 40 and exits the fluid inlet tube 10 at
the exit end 12. The fluid 5 flow then strikes an ultraviolet (UV)
window lower surface 36, which forms a portion of the lower end of
fluid containment vessel 30. Next, the fluid 5 flow is redirected
to the fluid outlet tube 50, which is located in the upper end of
the fluid containment vessel 30.
[0092] The fluid 5 is contained within the fluid containment vessel
30. The fluid containment vessel 30 includes an inner tube 33,
which may be constructed from UV-grade fused silica, contained
within an outer aluminum shell with a reflective interior surface
defining a UV mirror 31, with an air gap 32 between the outer shell
and the inner tube 33. The ends of the outer tube 30 are closed off
with the lower ultraviolet window surface 36 and an ultraviolet
window upper surface 37.
[0093] The preferred orientation of the ultraviolet (UV) water
disinfecting device is vertical, so that the fluid 5 flow
approximates plug-flow, and the position of the fluid outlet tube
50 is oriented to allow for quick and efficient removal of
undesirable air bubbles. Air bubbles present (e.g. induced by pump
vanes) in the fluid 5 can form scattering sites for the UV
radiation thereby degrading system efficiency. These UV scattering
sites result in UV radiation being directed at less than optimum
angles causing reflections from the fluid containment vessel
internal surface, the ultraviolet mirror 31 that is approximately
86% reflective when composed of aluminum tube. Without these UV
scattering sites, the ultraviolet radiation is dissipated mostly
within the fluid 5, because all reflections are near loss-less due
to of the total internal reflection (TIR) operation of a light
pipe. There is, however, a side-benefit from a degree of
scattering, and that is an improvement in the uniformity of the UV
light throughout the device, the theory of which is described in
"Brighter Backlights Using Highly Scattered Optical-Transmission
Polymer" (Horibe, et al, pg. 379-381, Society of Information
Display, paper 24.2, SID 1995 Digest). The degree of scattering can
be optimized, for example, using any suitable ray-trace program,
such as ASAP from Breault Research (Tucson, Ariz.).
[0094] Referring next to FIG. 3, a light pipe 100 region is formed
from the fluid 5, such as water, the fluid inlet tube 10, such as a
UV-grade fused silica tube, and the concentric gap 15, such as an
air gap or a vacuum gap. The concentric gap 15 is hydraulically
isolated from the fluid 5, in order to allow the light pipe 100 to
operate. Light pipe operation is based on the refractive index of
the concentric gap being less than the refractive index of the
fluid 5. The refractive indices of fused silica and water in the UV
region of the light spectrum are shown in Table 1 below.
TABLE-US-00001 TABLE 1 Fused Silica UV Grade (SiO2) Wavelength
Water (nm) Refractive Index Wavelength (nm) Refractive Index 170
1.615 172 1.568 185 1.575 185 1.493 200 1.550 200 1.452 214 1.534
215 1.427 280 1.494 280 1.379 302 1.487 305 1.370 436 1.467 450
1.344 546 1.460 550 1.336 656 1.456 650 1.331
[0095] As shown in Table 1, water has a lower refractive index as
UV grade Silica glass in the ultraviolet (UV) portion of the light
spectrum.
[0096] Ultraviolet (UV) radiation is transmitted from the high
intensity ultraviolet lamp 40, passes through the ultraviolet inlet
aperture 35, and enters the lower ultraviolet window surface 36 as
shown in FIG. 2. A first UV light ray 71 exits lower ultraviolet
window surface, is bent by refraction, and enters the fluid 5,
defining a second UV light ray 72. The second UV light ray 72
impinges upon the internal surface 13 of the fluid inlet tube 10,
which is in contact with the fluid 5, at an incidence angle 1,
where incidence angle 1 is measured with reference to the surface
normal of internal surface 13. As the second UV light ray 72 enters
a sidewall of the fluid inlet tube 10, it is bent by refraction and
redirected at a new internal reflection angle 2, defining a third
UV light ray 73.
[0097] The value of angle 2 is a function of incident angle 1 and
the refractive indices of the fluid 5 and the material, such as
UV-grade silica, from which the fluid inlet tube 10 is constructed.
The third UV light ray 73 continues through the fluid inlet tube 10
material and impinges upon the external surface 14 of the fluid
inlet tube that is in contact with the concentric gap 15. The third
UV light ray 73 is reflected back into the sidewall of the fluid
inlet tube 10, defining a fourth UV light ray 74 when the
refractive indices of the fluid inlet tube 10 material and the
concentric gap 15 meet certain conditions as defined by Snell's
Law. The refractive index of the concentric gap 15 is defined by
the material contained in the concentric gap or by the refractive
index of a vacuum if no material is contained within the concentric
gap 15.
[0098] It is a feature of the first embodiment of my invention that
a light pipe 100 region exists for at least part of the length of
the fluid inlet tube 10. Therefore, it is required that the
incidence angle 2 be limited to a predetermined range in accordance
with the refractive indices of the fluid 5, the material from which
the fluid inlet tube 10 is constructed, and the concentric gap 15.
In a preferred embodiment of my invention, the fluid inlet tube 10
is constructed from UV-grade silica glass, the fluid 5 to be
disinfected is water, and the concentric gap 15 contains a
vacuum.
[0099] Turning now to FIGS. 4 and 5, there is depicted a second
embodiment of my invention, wherein, unlike the first embodiment,
the fluid, such as water, enters my apparatus at one end thereof
and exits from the other end. The apparatus comprises an outer
containment vessel 80, which may as depicted have a square or
polygonal cross section or be of tubular or other configuration,
and which is advantageously of a metal with reflective inner wall
surface or surfaces 85, such as made from mirror-finished anodized
aluminum. At one end the vessel 80 has an input nozzle 81 for
receiving the fluid to be purified or disinfected, and at the other
end are four exit ports 83, each located on one of the four sides
of the vessel 80. Note that light pipes having square or polygonal
cross sections are known to homogenize light over a shorter
distance than circular-cross section light pipes (see U.S. Pat.
Nos. 3,170,980 and 5,341,445 as well as "The Use of a Kaleidoscope
to Obtain Uniform Flux Over a Large Area in a Solar Arc Imaging
Furnace", M. M. Chen et al., Applied Optics, March 1963, Vol. 2,
No.3), and so certain applications may benefit from this geometry,
although such a geometry may be more expensive to fabricate than
circular light pipes.
[0100] As seen in FIG. 5, located within the vessel 80 and sealed
thereto is an inner UV transmissive tube 86, which may also be
either square or tubular, which advantageously may be of UV-grade
fused silica, and which defines the fluid chamber 91 of this
embodiment. The inner UV transmissive tube 86 has a glass window 87
at its base and against which an ultraviolet flash lamp 88 is
pressed to minimize absorption in air of the ultraviolet
wavelengths below 200 nanometers (see FIGS. 10, 11a & 11b).
[0101] The inner UV transmissive tube 86 thus defines the fluid
chamber 91 for my apparatus and with the inner surface or surfaces
85 of the vessel 80 defines a gap 90 which advantageously is kept
to a minimum size while avoiding any contact between the inner
surface 85 of the vessel 80 and the inner UV transmissive tube 86.
The tube 86 and the gap 90 define walls for the fluid chamber 91.
Advantageously, the inner UV transmissive tube 86 also has a
minimal glass thickness consistent with sufficient strength to
resist breakage, the minimal thickness minimizing ultraviolet
absorption within the glass tubing. The minimal thickness of the
inner UV transmissive tube 86 can be helped with supplemental
internal support for the tubing, however such support must avoid
interfering with the total internal reflections of the ultraviolet
radiation within the inner tubing fluid chamber 91. As an example,
a narrow wire can be wrapped around the outside of the glass
tubing, having only point-contacts with the glass. An aluminum
reflector is then wrapped around the wire, thereby forming an air
gap between the aluminum and the glass, preserving TIR. The
structure can be further supported by a pressure-containing
structure (e.g. steel tube), which can be compressed against the
aluminum via a thin compliant material to accommodate the
differences in expansion & contraction of the various
materials.
[0102] The gap 90 between the inner surface of the inner internally
reflecting inner surface of the housing or vessel 80 and the outer
surface of the inner UV transmissive tube 86, which also serves as
a fluid chamber, advantageously contains a vacuum or may be filled
with a material assuring a refractive index of less than the
refractive index of the fluid passing within the inner UV
transmissive tube 86.
[0103] As with my first embodiment, the water or fluid to be
purified has a first refractive index while inner UV transmissive
tube 86 which defines the fluid chamber 91 for the water or other
fluid has a second refractive index, with the gap 90 between the
inner surface 85 of the housing and the inner UV transmissive tube
86 having a third refractive index. These first, second, and third
refractive indices are such that the ultraviolet radiation is
propagated within the inner UV transmissive tube 86 defining the
fluid chamber 91 via total internal reflection. As depicted in FIG.
5, arrows 94 show the fluid flow while the total internally
reflected ultraviolet radiation is shown by arrows 95 going in the
opposite direction to the arrows 94. Specifically, the fluid has a
refractive index n1 and the walls of the fluid chamber comprising
the tube 86 and the gap 90 have a collective refractive index n2
with n2 being less than n1.
[0104] Referring now to FIG. 6, there is shown an alternate
embodiment of the present invention comprising a plate-and-frame
construction. Water flows into pressurized water cavity 191 through
one of the slotted aperture shaped water inlets 181. After
ultraviolet (UV) irradiation as described above, water exits the
pressurized water cavity 191 via one of the slotted aperture shaped
water outlets 182. In one embodiment, there are four slotted
aperture shaped inlets 181 and four slotted aperture shaped outlets
182 where each of these inlets and outlets is connected to a
stainless steel adapter that includes standard threads for hose
fittings to potable water sources.
[0105] The pressured water cavity 191 is formed by stainless steel
support structure 101, which includes several windows cut
therethrough. Each of these windows is installed from within the
pressurized water cavity 191 region so that during operation, water
pressure forces a seal between the windows and the stainless steel
support structure 101. The ultraviolet radiation (UV) source 188,
such as a xenon lamp is mounted adjacent to the stainless steel
support structure 101 at the outlet port 182 region and the UV
radiation emitted therefrom enters the pressurized water cavity 191
through an apertured aluminum mirror coated UV window 187 bonded in
a groove portion of the stainless steel support structure 101. At
the inlet port 181 region of the stainless steel support structure
101 a mirror coated UV window 186 with an aluminum coating on the
air side is bonded in a groove. UV sidewall glass plates 185 are
bonded in grooves contained within sidewalls of the stainless steel
support structure 101. In a further embodiment, all metal to glass
and metal to metal joints are sealed with caulk and/or
adhesive.
[0106] In FIG. 7, there is shown a further embodiment of my
invention comprising a hollow helical coiled light pipe
construction with a side-coupling optic that is similar to a
configuration taught in U.S. Pat. No. 6,263,003. Alternate
side-coupling techniques are also taught in U.S. Pat. Nos.
5,058,980, 5,923,694, 6,370,297, and 6,625,354. For a coiled UV
disinfection system, such as the embodiment shown in FIG. 7 the
losses due to TIR leakage are useful in determining the source
power required for the input UV radiation 295. More specifically,
the embodiment of FIG. 7 shows input UV radiation 295 being coupled
into coiled tubing 210 via a non-UV absorbing coupling prism 202.
The UV radiation is contained within the coiled tubing 210 by TIR
because the material of the coiled tubing 210, such as UV-grade
fused silica glass, has a higher refractive index than the
surrounding medium 220, such as air or a vacuum. The ratio r
between the bend radius of the coil and the coiled tubing radius R
is advantageously is greater than 5:1 in order to ensure high
efficiency.
[0107] The coiled light pipe embodiment shown in FIG. 7 disinfects
water that flows in through water inlet 281, circulates through
coiled tubing 210, and exits through water outlet 282. Such
disinfection is accomplished by exposing biological material
contained within the water to the ultraviolet radiation that is
conducted by total internal reflection (TIR) in accordance with my
invention and as described above. As is well known, such biological
material includes nucleic acid components such as deoxyribonucleic
acid (DNA) or ribonucleic acid (RNA).
[0108] If the operating pressure of fluids to be disinfected is
high enough, the coiled tubing 210 may be strengthened to preclude
the coil from rupturing. An example strengthening material is an
exterior wire braid. In a preferred embodiment, the external wire
braid is further wrapped with aluminum foil to recycle TIR-leakage
back into the fluid.
[0109] Referring now to FIG. 8, there is shown a further
illustrative embodiment of my invention comprising a canteen 300
with a screw cap 301 covering an inlet fill tube 382. A coiled tube
310 circumferentially surrounds the fill tube 302. In operation,
the canteen 300 is filled with water 391 via the fill tube 302.
Advantageously, the fill tube 302 can be fitted with a filter (not
shown).
[0110] Water 391 contained within canteen 300 is disinfected by
ultraviolet radiation 395 emitted from UV source 388, such as a UV
light emitting diode (LED) or laser diode as follows. The water 391
enters the coiled tubing 310 via water inlet 381 which is
optionally provided with a sediment filter 321 such as wire mesh
filters avialable from Genesis Filtration Inc. (Rancho Cucamonga,
Calif.) and Martin Kurz & Co., Inc. (Mineola, N.Y.). In order
to allow water 391 to enter the water inlet 381, air 39 2 is
introduced into the canteen 300 via air vent tube 303 which has
water-blocking/air-passing membrane vents 304 at both ends. A
suitable water-blocking/air-passing membrane is available from
obtained from W. L. Gore & Associates, Inc (Fenton, Mo.).
Purified water exits the coiled tubing 310 (as well as the canteen
300) via water outlet 382. During periods when the canteen is not
providing water, a screw cap or other suitable shutoff is fitted to
water outlet 382.
[0111] The main UV-water interaction occurs by total internal
reflection (TIR) within the coiled tubing 310 as previously
described for FIG. 7. In the particular embodiment shown in FIG. 8,
the ultraviolet radiation 395 is end-launched into the coiled
tubing 310, although other embodiments are contemplated that use
side-launched ultraviolet radiation, such as shown in FIG. 7.
[0112] FIG. 9 shows wavelength-based plots for flashlamp excitation
and nucleic acid absorption in the ultraviolet region of the
electromagnetic spectrum. FIG. 9 also details the ultraviolet
absorption of UV-grade glasses such as Suprasil from Heraeus and
`021 grade` and polymer materials such as Hyflon tubing from
Ausimont. Details for the Ausimont tubing includes data for tubing
having 0.1 mm, 1 mm, and 2.5 mm thickness respectively.
[0113] There are other high intensity UV sources beyond flashlamps
known in the art, such semiconductor sources can be found at the
Defense Advanced Research Projects Agency (DARPA) Semiconductor UV
Optical Sources (SUVOS) website,
http://www.darpa.mil/mto/suvos/summaries.html. Semiconductor
sources are especially applicable to portable embodiments of the
present invention, such as the canteen shown in FIG. 8.
[0114] Refer now to FIGS. 10 and 11 which illustrate the key design
parameters for three sidewall configurations that are applicable to
certain embodiments of the present invention. The selected sidewall
configurations considered the effects of near-lossless TIR effect
as well as mirror reflections from aluminum and stainless steel. In
addition, variable water UV absorption coefficients of 0.008/cm and
0.125/cm repesctively were considered where such absorption was due
to biological content only. For simplicity, losses due to natural
absorption of UV within water are disregarded.
[0115] It thus is obvious to see that the area under each curve,
shown in FIGS. 10 and 11, gives a visual indication of how the
optical characteristics of a vessel effect the UV dosage efficacy
(i.e. dosage per electrical watt of input power) independent of
other factors discussed previously.
[0116] An average dosage calculation was made for each
configuration of near-loss TIR and wall material, shown in FIG. 10
by multiplying the intensity at each interval by the length of the
interval, computing the sum over an 87.75'' path length, and then
dividing the sum by 87.75 inches.
[0117] In FIG. 10 there is shown a graph illustrating the effects
of sidewall reflection over the path length where UV radiation
interacts with the fluid, such as water, that is being disinfected.
This graph assumes the UV radiation is launched from a point in the
center of a hypothetical fluid vessel, makes its first interaction
with the sidewall at a distance of 2.25 inches, and thereafter
interacts with the sidewall every 4.5 inches (these dimensions
selected as a rough estimate of the average path length of a ray
within an approximately 3-inch inside diameter vessel.
[0118] FIG. 11 is identical to FIG. 10 with the exception that the
average path length has been changed from 4.5 inches to 2.25
inches.
Alternate Embodiments
[0119] Alternate embodiments may be devised without departing from
the spirit or the scope of the invention. For example, water within
coiled tubing can be disinfected by ultraviolet radiation contained
by total internal reflection using equipment that can be scaled up
or down to many purification applications. Also, fluids other than
water can be purified using the present invention.
* * * * *
References